#if HAS_SPAN
using System.Buffers;
#endif
using System.IO.Compression;
using static QRCoder.QRCodeGenerator;

namespace QRCoder;

/// <summary>
/// Represents a QR code generator that outputs QR codes as PNG byte arrays.
/// </summary>
public sealed class PngByteQRCode : AbstractQRCode, IDisposable
{
    /// <summary>
    /// Initializes a new instance of the <see cref="PngByteQRCode"/> class.
    /// Constructor without parameters to be used in COM objects connections.
    /// </summary>
    public PngByteQRCode() { }

    /// <summary>
    /// Initializes a new instance of the <see cref="PngByteQRCode"/> class with the specified <see cref="QRCodeData"/>.
    /// </summary>
    /// <param name="data"><see cref="QRCodeData"/> generated by the QRCodeGenerator.</param>
    public PngByteQRCode(QRCodeData data) : base(data)
    {
    }


    /// <summary>
    /// Creates a black and white PNG of the QR code, using 1-bit grayscale.
    /// </summary>
    /// <param name="pixelsPerModule">The number of pixels each dark/light module of the QR code will occupy in the final QR code image.</param>
    /// <param name="drawQuietZones">Indicates if quiet zones around the QR code should be drawn.</param>
    /// <returns>Returns the QR code graphic as a PNG byte array.</returns>
    public byte[] GetGraphic(int pixelsPerModule, bool drawQuietZones = true)
    {
        using var png = new PngBuilder();
        var size = (QrCodeData.ModuleMatrix.Count - (drawQuietZones ? 0 : 8)) * pixelsPerModule;
        png.WriteHeader(size, size, 1, PngBuilder.ColorType.Greyscale);
        var scanLines = DrawScanlines(pixelsPerModule, drawQuietZones);
        png.WriteScanlines(scanLines);
#if HAS_SPAN
        ArrayPool<byte>.Shared.Return(scanLines.Array!);
#endif
        png.WriteEnd();
        return png.GetBytes();
    }

#if !NETSTANDARD1_3
    /// <summary>
    /// Creates a 2-color PNG of the QR code, using 1-bit indexed color. Colors may contain transparency.
    /// </summary>
    /// <param name="pixelsPerModule">The number of pixels each dark/light module of the QR code will occupy in the final QR code image.</param>
    /// <param name="darkColor">The color of the dark modules.</param>
    /// <param name="lightColor">The color of the light modules.</param>
    /// <param name="drawQuietZones">Indicates if quiet zones around the QR code should be drawn.</param>
    /// <returns>Returns the QR code graphic as a PNG byte array.</returns>
    public byte[] GetGraphic(int pixelsPerModule, System.Drawing.Color darkColor, System.Drawing.Color lightColor, bool drawQuietZones = true)
        => GetGraphic(pixelsPerModule, new byte[] { darkColor.R, darkColor.G, darkColor.B, darkColor.A }, new byte[] { lightColor.R, lightColor.G, lightColor.B, lightColor.A }, drawQuietZones);
#endif

    /// <summary>
    /// Creates a 2-color PNG of the QR code, using 1-bit indexed color. Accepts 3-byte RGB colors for normal images and 4-byte RGBA-colors for transparent images.
    /// </summary>
    /// <param name="pixelsPerModule">The number of pixels each dark/light module of the QR code will occupy in the final QR code image.</param>
    /// <param name="darkColorRgba">The color of the dark modules as an RGBA byte array.</param>
    /// <param name="lightColorRgba">The color of the light modules as an RGBA byte array.</param>
    /// <param name="drawQuietZones">Indicates if quiet zones around the QR code should be drawn.</param>
    /// <returns>Returns the QR code graphic as a PNG byte array.</returns>
    public byte[] GetGraphic(int pixelsPerModule, byte[] darkColorRgba, byte[] lightColorRgba, bool drawQuietZones = true)
    {
        using var png = new PngBuilder();
        var size = (QrCodeData.ModuleMatrix.Count - (drawQuietZones ? 0 : 8)) * pixelsPerModule;
        png.WriteHeader(size, size, 1, PngBuilder.ColorType.Indexed);
        png.WritePalette(darkColorRgba, lightColorRgba);
        var scanLines = DrawScanlines(pixelsPerModule, drawQuietZones);
        png.WriteScanlines(scanLines);
#if HAS_SPAN
        ArrayPool<byte>.Shared.Return(scanLines.Array!);
#endif
        png.WriteEnd();
        return png.GetBytes();
    }

    /// <summary>
    /// Creates a bitmap where each pixel is represented by a single bit, dark = 0 and light = 1.
    /// </summary>
    /// <param name="pixelsPerModule">The number of pixels each dark/light module of the QR code will occupy in the final QR code image.</param>
    /// <param name="drawQuietZones">Indicates if quiet zones around the QR code should be drawn.</param>
    /// <returns>Returns the bitmap as a byte array.</returns>
    private ArraySegment<byte> DrawScanlines(int pixelsPerModule, bool drawQuietZones)
    {
        var moduleMatrix = QrCodeData.ModuleMatrix;
        var matrixSize = moduleMatrix.Count - (drawQuietZones ? 0 : 8);
        var quietZoneOffset = (drawQuietZones ? 0 : 4);
        var bytesPerScanline = (matrixSize * pixelsPerModule + 7) / 8 + 1; // A monochrome scanline is one byte for filter type then one bit per pixel.
        var scanLinesLength = bytesPerScanline * matrixSize * pixelsPerModule;
#if HAS_SPAN
        var scanlines = ArrayPool<byte>.Shared.Rent(scanLinesLength);
        Array.Clear(scanlines, 0, scanLinesLength);
#else
        var scanlines = new byte[scanLinesLength];
#endif

        for (var y = 0; y < matrixSize; y++)
        {
            var modules = moduleMatrix[y + quietZoneOffset];
            var scanlineOffset = y * pixelsPerModule * bytesPerScanline;

            // Draw a scanline with the modules from the QR code.
            for (var x = 0; x < matrixSize; x++)
            {
                if (modules[x + quietZoneOffset])
                {
                    continue;
                }

                var pixelIndex = x * pixelsPerModule;
                var endIndex = pixelIndex + pixelsPerModule;
                for (; pixelIndex < endIndex; pixelIndex++)
                {
                    scanlines[scanlineOffset + 1 + pixelIndex / 8] |= (byte)(0x80 >> (pixelIndex % 8));
                }
            }

            // Copy the scanline the required number of times.
            for (var copyCount = 1; copyCount < pixelsPerModule; copyCount++)
            {
                Array.Copy(scanlines, scanlineOffset, scanlines, scanlineOffset + copyCount * bytesPerScanline, bytesPerScanline);
            }
        }

        return new ArraySegment<byte>(scanlines, 0, scanLinesLength);
    }

    /// <summary>
    /// Writes the chunks that make up a PNG file.
    /// </summary>
    /// <remarks>
    /// See https://www.w3.org/TR/2003/REC-PNG-20031110 and https://www.ietf.org/rfc/rfc1950.txt.
    /// </remarks>
    private sealed class PngBuilder : IDisposable
    {
        private static readonly byte[] _pngSignature = { 0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A };

        private static readonly uint[] _crcTable = {
            0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA, 0x076DC419, 0x706AF48F, 0xE963A535, 0x9E6495A3, 0x0EDB8832, 0x79DCB8A4, 0xE0D5E91E, 0x97D2D988, 0x09B64C2B, 0x7EB17CBD, 0xE7B82D07, 0x90BF1D91, 0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE, 0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7, 0x136C9856, 0x646BA8C0, 0xFD62F97A, 0x8A65C9EC, 0x14015C4F, 0x63066CD9, 0xFA0F3D63, 0x8D080DF5, 0x3B6E20C8, 0x4C69105E, 0xD56041E4, 0xA2677172, 0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B, 0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940, 0x32D86CE3, 0x45DF5C75, 0xDCD60DCF, 0xABD13D59, 0x26D930AC, 0x51DE003A, 0xC8D75180, 0xBFD06116, 0x21B4F4B5, 0x56B3C423, 0xCFBA9599, 0xB8BDA50F, 0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924, 0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D,
            0x76DC4190, 0x01DB7106, 0x98D220BC, 0xEFD5102A, 0x71B18589, 0x06B6B51F, 0x9FBFE4A5, 0xE8B8D433, 0x7807C9A2, 0x0F00F934, 0x9609A88E, 0xE10E9818, 0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01, 0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E, 0x6C0695ED, 0x1B01A57B, 0x8208F4C1, 0xF50FC457, 0x65B0D9C6, 0x12B7E950, 0x8BBEB8EA, 0xFCB9887C, 0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3, 0xFBD44C65, 0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2, 0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB, 0x4369E96A, 0x346ED9FC, 0xAD678846, 0xDA60B8D0, 0x44042D73, 0x33031DE5, 0xAA0A4C5F, 0xDD0D7CC9, 0x5005713C, 0x270241AA, 0xBE0B1010, 0xC90C2086, 0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F, 0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4, 0x59B33D17, 0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD,
            0xEDB88320, 0x9ABFB3B6, 0x03B6E20C, 0x74B1D29A, 0xEAD54739, 0x9DD277AF, 0x04DB2615, 0x73DC1683, 0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8, 0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1, 0xF00F9344, 0x8708A3D2, 0x1E01F268, 0x6906C2FE, 0xF762575D, 0x806567CB, 0x196C3671, 0x6E6B06E7, 0xFED41B76, 0x89D32BE0, 0x10DA7A5A, 0x67DD4ACC, 0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5, 0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252, 0xD1BB67F1, 0xA6BC5767, 0x3FB506DD, 0x48B2364B, 0xD80D2BDA, 0xAF0A1B4C, 0x36034AF6, 0x41047A60, 0xDF60EFC3, 0xA867DF55, 0x316E8EEF, 0x4669BE79, 0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236, 0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F, 0xC5BA3BBE, 0xB2BD0B28, 0x2BB45A92, 0x5CB36A04, 0xC2D7FFA7, 0xB5D0CF31, 0x2CD99E8B, 0x5BDEAE1D,
            0x9B64C2B0, 0xEC63F226, 0x756AA39C, 0x026D930A, 0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713, 0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38, 0x92D28E9B, 0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21, 0x86D3D2D4, 0xF1D4E242, 0x68DDB3F8, 0x1FDA836E, 0x81BE16CD, 0xF6B9265B, 0x6FB077E1, 0x18B74777, 0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C, 0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45, 0xA00AE278, 0xD70DD2EE, 0x4E048354, 0x3903B3C2, 0xA7672661, 0xD06016F7, 0x4969474D, 0x3E6E77DB, 0xAED16A4A, 0xD9D65ADC, 0x40DF0B66, 0x37D83BF0, 0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9, 0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6, 0xBAD03605, 0xCDD70693, 0x54DE5729, 0x23D967BF, 0xB3667A2E, 0xC4614AB8, 0x5D681B02, 0x2A6F2B94, 0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B, 0x2D02EF8D
        };

        // ReSharper disable InconsistentNaming
        // Chunk types
        private static readonly byte[] _ihdr = { 73, 72, 68, 82 };

        private static readonly byte[] _idat = { 73, 68, 65, 84 };

        private static readonly byte[] _iend = { 73, 69, 78, 68 };

        private static readonly byte[] _plte = { 80, 76, 84, 69 };

        private static readonly byte[] _trns = { 116, 82, 78, 83 };
        // ReSharper enable InconsistentNaming

        public enum ColorType : byte
        {
            Greyscale = 0,
            Indexed = 3
        }

        private MemoryStream _stream = new MemoryStream();

        public void Dispose()
        {
            _stream?.Dispose();
            _stream = null!;
        }

        public byte[] GetBytes()
        {
            var bytes = _stream.ToArray();

            // Enumerate chunks in file and insert their CRC32 checksums.
            var chunkOffset = _pngSignature.Length;
            while (chunkOffset < bytes.Length)
            {
                // Read length field.
                var dataLength = (bytes[chunkOffset] << 24) | (bytes[chunkOffset + 1] << 16) | (bytes[chunkOffset + 2] << 8) | bytes[chunkOffset + 3];

                // CRC is computed from type and data fields.
                var crc = Crc32(bytes, chunkOffset + 4, dataLength + 4);

                // Write CRC to end of chunk.
                var crcOffset = chunkOffset + 8 + dataLength;
                bytes[crcOffset + 0] = (byte)(crc >> 24);
                bytes[crcOffset + 1] = (byte)(crc >> 16);
                bytes[crcOffset + 2] = (byte)(crc >> 8);
                bytes[crcOffset + 3] = (byte)crc;

                // Seek to next chunk.
                chunkOffset = crcOffset + 4;
            }

            return bytes;
        }

        /// <summary>
        /// Writes the IHDR chunk. This must be the first chunk in the file.
        /// </summary>
        public void WriteHeader(int width, int height, byte bitDepth, ColorType colorType)
        {
            _stream.Write(_pngSignature, 0, _pngSignature.Length);
            WriteChunkStart(_ihdr, 13);

            // Size.
            WriteIntBigEndian((uint)width);
            WriteIntBigEndian((uint)height);

            // Color.
            _stream.WriteByte(bitDepth);
            _stream.WriteByte((byte)colorType);

            // Constants.
            _stream.WriteByte(0);
            _stream.WriteByte(0);
            _stream.WriteByte(0);

            WriteChunkEnd();
        }

        /// <summary>
        /// Writes the PLTE chunk, and also the tRNS chunk if necessary. Must come before the IDAT chunk.
        /// </summary>
        public void WritePalette(params byte[][] rgbaColors)
        {
            const int Red = 0, Green = 1, Blue = 2, Alpha = 3;
            const byte Opaque = 255;
            var hasAlpha = false;

            WriteChunkStart(_plte, 3 * rgbaColors.Length);
            foreach (var color in rgbaColors)
            {
                hasAlpha |= color.Length > Alpha && color[Alpha] < Opaque;
                _stream.WriteByte(color[Red]);
                _stream.WriteByte(color[Green]);
                _stream.WriteByte(color[Blue]);
            }
            WriteChunkEnd();

            if (!hasAlpha)
            {
                return;
            }

            WriteChunkStart(_trns, rgbaColors.Length);
            foreach (var color in rgbaColors)
            {
                _stream.WriteByte(color.Length > Alpha ? color[Alpha] : Opaque);
            }
            WriteChunkEnd();
        }

        /// <summary>
        /// Writes the IDAT chunk with the actual picture.
        /// </summary>
        public void WriteScanlines(ArraySegment<byte> scanlines)
        {
            using var idatStream = new MemoryStream();
            Deflate(idatStream, scanlines);

            WriteChunkStart(_idat, (int)(idatStream.Length + 6));

            // Deflate header.
            _stream.WriteByte(0x78); // 8 Deflate algorithm, 7 max window size
            _stream.WriteByte(0x9C); // Check bits.

            // Compressed data.
            idatStream.WriteTo(_stream);
            // Deflate checksum.
            var adler = Adler32(scanlines.Array!, 0, scanlines.Count);
            WriteIntBigEndian(adler);

            WriteChunkEnd();
        }

        /// <summary>
        /// Writes the IEND chunk. This must be the last chunk in the file.
        /// </summary>
        public void WriteEnd()
        {
            WriteChunkStart(_iend, 0);
            WriteChunkEnd();
        }

        private void WriteChunkStart(byte[] type, int length)
        {
            WriteIntBigEndian((uint)length);
            _stream.Write(type, 0, 4);
        }

        private void WriteChunkEnd()
        {
            // Reserves 4 bytes space for crc32 so GetBytes can add it later.
            _stream.SetLength(_stream.Length + 4);
            _stream.Position += 4;
        }

        private void WriteIntBigEndian(uint value)
        {
            _stream.WriteByte((byte)(value >> 24));
            _stream.WriteByte((byte)(value >> 16));
            _stream.WriteByte((byte)(value >> 8));
            _stream.WriteByte((byte)value);
        }

        private static void Deflate(Stream output, ArraySegment<byte> bytes)
        {
            using var deflateStream = new DeflateStream(output, CompressionMode.Compress, leaveOpen: true);
            deflateStream.Write(bytes.Array!, 0, bytes.Count);
        }

        // Reference implementation from RFC 1950. Not optimized.
        private static uint Adler32(byte[] data, int index, int length)
        {
            const uint Base = 65521;
            uint s1 = 1, s2 = 0;

            var end = index + length;
            for (var n = index; n < end; n++)
            {
                s1 = (s1 + data[n]) % Base;
                s2 = (s2 + s1) % Base;
            }

            return (s2 << 16) + s1;
        }

        // Reference implementation from REC-PNG-20031110. Not optimized.
        private static uint Crc32(byte[] data, int index, int length)
        {
            var c = 0xffffffff;

            var end = index + length;
            for (var n = index; n < end; n++)
            {
                c = _crcTable[(c ^ data[n]) & 0xff] ^ (c >> 8);
            }

            return c ^ 0xffffffff;
        }
    }
}

/// <summary>
/// Provides static methods for creating PNG byte array QR codes.
/// </summary>
public static class PngByteQRCodeHelper
{
    /// <summary>
    /// Creates a PNG byte array QR code with a single function call.
    /// </summary>
    /// <param name="plainText">The text or payload to be encoded inside the QR code.</param>
    /// <param name="pixelsPerModule">The number of pixels each dark/light module of the QR code will occupy in the final QR code image.</param>
    /// <param name="darkColorRgba">The color of the dark modules as an RGBA byte array.</param>
    /// <param name="lightColorRgba">The color of the light modules as an RGBA byte array.</param>
    /// <param name="eccLevel">The level of error correction data.</param>
    /// <param name="forceUtf8">Specifies whether the generator should be forced to work in UTF-8 mode.</param>
    /// <param name="utf8BOM">Specifies whether the byte-order-mark should be used.</param>
    /// <param name="eciMode">Specifies which ECI mode should be used.</param>
    /// <param name="requestedVersion">Sets the fixed QR code target version.</param>
    /// <param name="drawQuietZones">Indicates if quiet zones around the QR code should be drawn.</param>
    /// <returns>Returns the QR code graphic as a PNG byte array.</returns>
    public static byte[] GetQRCode(string plainText, int pixelsPerModule, byte[] darkColorRgba, byte[] lightColorRgba, ECCLevel eccLevel, bool forceUtf8 = false, bool utf8BOM = false, EciMode eciMode = EciMode.Default, int requestedVersion = -1, bool drawQuietZones = true)
    {
        using var qrGenerator = new QRCodeGenerator();
        using var qrCodeData = qrGenerator.CreateQrCode(plainText, eccLevel, forceUtf8, utf8BOM, eciMode, requestedVersion);
        using var qrCode = new PngByteQRCode(qrCodeData);
        return qrCode.GetGraphic(pixelsPerModule, darkColorRgba, lightColorRgba, drawQuietZones);
    }



    /// <summary>
    /// Creates a PNG byte array QR code with a single function call.
    /// </summary>
    /// <param name="txt">The text or payload to be encoded inside the QR code.</param>
    /// <param name="eccLevel">The level of error correction data.</param>
    /// <param name="size">The number of pixels each dark/light module of the QR code will occupy in the final QR code image.</param>
    /// <param name="drawQuietZones">Indicates if quiet zones around the QR code should be drawn.</param>
    /// <returns>Returns the QR code graphic as a PNG byte array.</returns>
    public static byte[] GetQRCode(string txt, QRCodeGenerator.ECCLevel eccLevel, int size, bool drawQuietZones = true)
    {
        using var qrGen = new QRCodeGenerator();
        using var qrCode = qrGen.CreateQrCode(txt, eccLevel);
        using var qrPng = new PngByteQRCode(qrCode);
        return qrPng.GetGraphic(size, drawQuietZones);
    }
}
